<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .dropdown {
        /* Border */
        border: 1px solid rgba(0, 0, 0, 0.3);
        display: flex;

        /* Reset list styles */
        list-style-type: none;
        margin: 0;
        padding: 0;
      }

      .dropdown li {
        /* Spacing */
        padding: 8px;

        /* Used to position the sub dropdown */
        position: relative;
      }

      /* The sub dropdown */
      .dropdown ul {
        /* Border */
        border: 1px solid rgba(0, 0, 0, 0.3);

        /* Hidden by default */
        display: none;

        /* Absolute position */
        left: 0;
        position: absolute;
        top: 100%;

        /* Reset styles */
        list-style-type: none;
        margin: 0;
        padding: 0;

        /* Width */
        width: 200px;
      }

      /* The second level sub dropdown */
      .dropdown ul ul {
        left: 100%;
        position: absolute;
        top: 0;
      }

      /* Change background color of list item when being hovered */
      .dropdown li:hover {
        background-color: rgba(0, 0, 0, 0.1);
      }

      /* Show the direct sub dropdown when hovering the list item */
      .dropdown li:hover > ul {
        display: block;
      }
    </style>
  </head>
  <body>
    <ul class="dropdown">
      <li>Home</li>
      <li>
        <div>Patterns</div>
        <!-- First level sub dropdown -->
        <ul>
          <li>Layout</li>
          <li>Input</li>
          <li>
            <div>Navigation</div>
            <!-- Second level sub dropdown -->
            <ul>
              <li>Breadcrumb</li>
              <li>Dropdown</li>
              <li>Menu</li>
              <li>Nested dropdown</li>
            </ul>
          </li>
          <li>Display</li>
          <li>Feedback</li>
        </ul>
      </li>
      <li>Products</li>
      <li>About</li>
    </ul>
  </body>
</html>
